Orthogonal Variability Model

The orthogonal variability model defines variability in a separate model to
other domain artefacts.

As such it can be linked to all types of artefacts. This can be contrasted
with other methods of variability management, such as FODA, where variability
is mixed into the feature model. Benefits of the OVM approach are that
variability does not get spread across models, and already complex models do
not get overloaded with variability concepts.

Basically, you model the variability outside of all your other models, and link
it into them via artefact dependencies. I like this idea, as you can use your
one variability model with all your different models.